Portable electronic devices having touch screens, such as a touch sensitive surface overlaying a display, are well known in the art. Examples of touch screen devices include smartphones, tablets, media players and portable gaming devices. A touch screen device utilizes the touch screen as its user interface or one of its user interfaces. The device may provide one or more functions activated or managed by a user's interaction with the touch screen of the device. Examples of such functions include input and output of media, (such as images, video, audio, and multimedia), messaging, web browsing and wireless communication.
A touch screen has a sensor that can detect “touch” by a user at a display. The term “touch” refers to contact at or near a surface of the display with a user's digit or hand. Touch screens generally require active monitoring of the touch screen sensor to detect contact. In order to ensure detection, touch screen devices typically provide some level of power to the sensor on the continual or periodic basis, thus causing significant power consumption. For example, a resistive touch screen has electrically-resistive layers separated by a thin space, in which at least one layer is provided electrical current on a continual or periodic basis. When a user presses touch screen, the electrically-resistive layers contact and a controller determines the location of contact based on an analysis of the detected voltage. As another example, a capacitive touch screen has an insulator coated with a conductor, in which electrical current is provided to generate an electrostatic field. When a user touches the surface of the capacitive touch screen, the user acts as an electrical conductor that results in a distortion of the electrostatic field of the touch screen.
Touch screen devices generally utilize switches, separate from the touch screen, for powering-on or waking devices. Switches interrupt or divert electrical current, and a typical switch is an electromechanical component having electrical contacts connected to external circuits. A switch can control the flow of power from a power source to another component. For a typical touch screen device, the switch may be activated manually by pressing-and-holding a power button, separate from the touch screen, for a certain period of time. Similarly, the device may be awaken from a sleep mode by simply pressing the power button. Operation of a switch consumes less power than operation of a touch screen, which requires active monitoring.